I've been hearing about the impending "conservative crackup" for nearly 25 years. The term was coined by R. Emmett Tyrrell Jr., the founder of the American Spectator. He meant that conservatism had lost its philosophical coherence. But the phrase almost instantly became a catchall for any prediction of the right's imminent demise or dissolution.

These dire prophesies always reminded me of those "Free Beer Tomorrow" signs. As Annie sings, tomorrow is "always a day away."

Well, thanks to Donald Trump, tomorrow may be here. There's a fierce internecine battle over whether to oppose Trump's run, passively accept his popularity, or zealously support his bid.

The level of distrust among many of the different factions of the conservative coalition has never been higher, at least not in my experience. Arguments don't seem to matter, only motives do.

Here's Rush Limbaugh on Friday: "Forget the name is Trump. If a candidate could [guarantee to] fix everything that's wrong in this country the way the Republican Party thinks it's wrong, if it were a slam dunk, if it were guaranteed, that candidate will still be opposed by the Republican Party establishment. ... If he's not part of the clique, they don't want him in there."

In other words, the GOP establishment has become so corrupted, its members would knowingly reject a savior just to protect their comfortable way of life.

Limbaugh also says that the conservative "intelligentsia" -- in the form of conservative magazines and think tanks -- doesn't want to solve problems, it just wants to score points in an "academic exercise" within a perpetual "debating society." "In other words," Limbaugh says, "some people constantly need something to run against as a reason to exist."

Meanwhile, many in the so-called establishment and intelligentsia have similar complaints about Limbaugh and his imitators on radio and cable TV, although most don't say it publicly for fear of reprisal. I've lost track of the number of congressmen, consultants and so forth who've told me that talk-radio hosts spend their time criticizing fellow conservatives because that's what brings in the highest ratings. (Beating up on liberals just doesn't animate the base like it used to.)

Wherever the truth lies, questioning motives is poisonous, because such claims are not only unfalsifiable, but they also give an instant excuse to ignore sincere, reasoned arguments.

Nearly every position on Trump is immediately subjected to a kind of vulgar Marxist analysis. "You think Trump would make a bad president? Oh, you're just saying that because you're part of the establishment!" "You think Trump would make a good president? Oh, you're just saying that to get attention."

National Review magazine, where I am a senior editor, recently published an issue arguing that Trump is unfit to be a conservative standard-bearer. Trump responded by saying we were a "failing paper." That's not remotely true (we're not even a paper), but even if it were, how does that refute our criticisms?

I'm not saying motives don't matter, but they're best left out of disagreements if you hope to persuade your ideological allies.

The one exception to this rule is when your opponents openly acknowledge their self-interest.

Last week, former Sen. Bob Dole, Sen. Orrin Hatch and a passel of consultants were quoted in the press giving Neville Chamberlain-like assurances that Trump was a man they could deal with while Ted Cruz was the real threat to their food bowls.

"Do they all love Trump? No," Republican lobbyist Richard F. Hohlt told the New York Times. "But there's a feeling that he is not going to layer over the party or install his own person. Whereas Cruz will have his own people there."

It's hard to criticize Limbaugh & Co. for cynically questioning the motives of the establishment when party apparatchiks confess them in the pages of the New York Times.

There's no shortage of reasons for why the right is at war over whether or not to take a flier on Trump. All of the various establishments and the counter-establishments overpromised and underdelivered in recent years. Congressional leaders talked a big game while campaigning but played small ball once re-elected. Cruz and his supporters accused his fellow politicians of being corrupt sellouts, and so many people believed him, they'd now rather take a gamble on Trump than back Cruz, a mere politician.